Kenwood CS-1045, Instruction Manual

Page: 31 / 35

X - Y A P P L I C A T I O N S
* Phase Shift Measurement
A method of phase measurement requires calculations bas-
ed on the Lissajous patterns obtained using X-Y operations.
Distortion due to non-linear amplification also can be
displayed.
A sine wave input is applied to the audio circuit being
tested. The same sine wave input is applied to the vertical
input of the oscilloscope, and the output of the tested cir-
cuit is applied to the horizontal input of the oscilloscope.
The amount of phase difference between the two signals
can be calculated from the resulting waveform.
To make phase measurements, use the following pro-
cedure.
1. Using an audio signal generator with a pure sinusoidal
signal, apply a sine wave test signal at the desired test
frequency to the audio network being tested.
2. Set the signal generator output for the normal operating
level of the circuit being tested. If desired, the circuit's
output may be observed on the oscilloscope. If the test
circuit is overdriven, the sine wave display on the
oscilloscope is clipped and the signal level must be
reduced.
3. Connect the channel 2 probe to the output of the test
circuit.
4. Select X - Y operation by placing the HORIZ MODE switch
in the X - Y position.
5. Connect the channel 1 probe to the input of the test cir-
cuit.
(The input and output test connections to the vertical
and horizontal oscilloscope inputs may be reserved.)
6. Adjust the channel 1 and 2 gain controls for a suitable
viewing size.
7. Some typical results are shown in Fig. 4 3 .
If the two signals are in phase, the oscilloscope trace is a
straight diagonal line. If the vertical and horizontal gain
are properly adjusted, this line is at a 4 5 ° angle. A 9 0 °
phase shift produces a circular oscilloscope pattern.
Phase shift of less (or more) than 9 0 ° produces an ellip-
tical oscilloscope pattern. The amount of phase shift
can be calculated from the oscilloscope trace as shown
in Fig. 4 2 .
Where </> = phase angle
* Frequency
Measurement
1. Connect the sine
wave
of known frequency to the chan-
nel 2 INPUT
jack
of the oscilloscope and select X — Y
operation. This provides external horizontal input.
2. Connect the vertical input probe (CH1 INPUT) to the
unknown frequency.
3. Adjust the channel 1 and 2 size controls for convenient,
easy-to-read size of display.
4. The resulting pattern, called a Lissajous pattern, shows
the ratio between the two frequencies.
Unknown frequency to
Vertical input, Standard
frequency to Horizontal
input
See note
See note
Ratio of unknown
to standard
1/2:1
1:1
1-1/2:1
6:1
Note: A n y one of these figures, depending
upon phase relationship
Fig. 4 4 Lissajous waveforms used for
frequency measurement
Fig. 4 2 Phase shift calculation
3 1
No amplitude distortion,
no out of phase
Amplitude distortion,
no out of phase
1 8 0 ° out of phase
No amplitude distortion,
out of phase
Amplitude distortion,
out of phase
9 0 ° out of phase
Fig.4S Typical phase measurement oscilloscope display
SINE
<j>= -|-